Recently, the demand for a transparent electrode in such fields as flat panel displays, touch panels, solar cells, etc. is increasing. The material for the transparent electrode which is currently being mainly used includes a metal oxide such as indium tin oxide (ITO) for vacuum deposition. However, because this metal oxide requires a post-treatment process at high temperature in order to exhibit high electrical conductivity, it is difficult to apply on a plastic substrate having comparatively low heat resistance. Even if a metal oxide film is formed on a plastic substrate through low-temperature deposition, problems of the metal oxide film easily cracking when faced with warping or other physical deformation may occur. Furthermore, vacuum deposition needs high production costs. Hence, thorough research into a transparent electrode material usable instead of the above material is being conducted.
Thus, there have been proposed methods of forming a transparent conductive film having high electrical conductivity and optical transparency by manufacturing a metal such as silver in the form of a nanostructure, dispersing the metal nanostructure in a solution and then applying the resulting dispersion solution on a plastic film. To this end, methods of simply manufacturing a metal nanostructure on a large scale using a solution are required, and the metal nanostructure should be provided in the form of wire having a high length-to-diameter ratio in order to form an effective conductive network. There have been recent reports about manufacturing metal nanowire from a metal salt precursor using a polyol such as ethyleneglycol as a reducing agent in the presence of polyvinylpyrrolidone (Chem. Mater. 14, 4736-4745). This technique is advantageous because the metal nanostructure is comparatively easily manufactured using a solution through the reaction, called “polyol reduction”. Although the metal nanostructure thus manufactured may have the shape of nanowire, it may further have the shape of nanoparticles, in addition to the shape of nanowire, and also the shape of the nanostructure is difficult to reproducibly manufacture depending on the reaction conditions.
Therefore, in the manufacturing of the metal nanostructure, there is a need for a method of uniformly and reproducibly manufacturing a final product in the form of nanowire.